A Data Booklet may be used.
An element can be a semiconductor if
On this basis, which elements are expected to be semiconductors?
Source: 2018 HCI J1 Promo P1 Q2
Which statement about the orbitals in a krypton atom is correct?
Source: CJC 2017 Promo, via EJC 2022 Atomic Structure Topical Revision, Q6
Nuclear theories predict that nuclei with these numbers of protons, or of neutrons, are especially stable: 2, 8, 20, 28, 50, 82, 126. The most stable nuclei have one of these numbers of protons and one of these numbers of neutrons.
Which isotope is the most stable?
Source: 2022 HCI J1 Promo P1 Q1
The deuteron is the nucleus of deuterium, 21D.
Source: 2024 RVHS J2 Prelim P2 Q1(a)
CommonParticles travelling at the same speed through an electric field of constant strength are deflected through an angle proportional to their charge to mass ratio. In one set-up, protons are deflected through +15°.
Source: 2022 JPJC J1 Year End P2 Q1(a)(iii) to (v)
CommonElement A is in Period 4. Its first eight ionisation energies, in kJ mol−1, are
947 1798 2735 4837 6043 12 310 14 300 16 800
Source: 2024 NJC J2 Prelim P2 Q1(a)
Source: 2024 VJC J2 Prelim P2 Q1(b)
Iron, copper and zinc are in Period 4 of the Periodic Table.
Cu+: 1s2 2s2 2p6 ............................................................
Zn+: 1s2 2s2 2p6 ............................................................
Source: 2022 HCI J1 Promo P2 Q1(b)
Source: 2024 HCI J2 Prelim P2 Q1(b), adapted
Source: 2021 RVHS J1 Common Test P2 Section A Q1(c)
Source: 2023 RI J2 Prelim P3 QA2(c)(i)
ChallengeSulfur in volcanic gases is mainly a mixture of the isotopes 32S and 34S. A sample enriched in 32S comes from deep mantle degassing (gas released from magma deep in the Earth's mantle), while a sample enriched in 34S comes from recycled hydrothermal sources.
| isotope | 32S | 33S | 34S | 36S |
|---|---|---|---|---|
| relative isotopic mass | 31.972 | 32.971 | 33.968 | 35.967 |
| abundance / % | 95.02 | 0.75 | 4.21 | 0.02 |
Source: 2025 EJC J2 Prelim P2 Q1(b)
B1 and 2 only[1]
Check each element's Group and recall its valence configuration.
CThe 3d subshell has five orbitals of the same energy in an isolated atom.[1]
C40Ca[1]
Find the proton number from the Data Booklet, then neutrons = nucleon number − proton number.
| 2He | 8Be | 40Ca | 210Pb | |
|---|---|---|---|---|
| protons | 2 | 4 | 20 | 82 |
| neutrons | 0 | 4 | 20 | 128 |
Only 40Ca has both numbers in the list.
Protons and deuterons are deflected towards the negative plate, but hydrogen atoms are not deflected. This is because protons and deuterons are positively charged, whereas hydrogen atoms are electrically neutral.[1]
The mass of a proton is half the mass of a deuteron (1 neutron and 1 proton), so the angle of deflection of protons is double that of deuterons.[1]
+1310 kJ mol−1 (the same value as the first ionisation energy of hydrogen)[1]
The electron to be removed from a deuterium atom and a hydrogen atom experiences the same nuclear charge and no shielding effect. They are at the same distance from the nucleus. Thus, the attraction of the positive nucleus for the (1s) electron to be removed is the same.[1]
orHydrogen and deuterium have the same electronic configuration. Although deuterium has an additional neutron, it has no charge, so it does not affect the attraction of the nucleus for the electron to be removed.
4He2+: chargemass = 2+4 = 1+2, half that of a proton
Angle = ½ × (+15°) = +7.50°[1]
q12 × (+15°) = +5°
q = 4+[1]
The mass of A is the mass of its protons and neutrons (electrons are very light), so number of neutrons = 12 − 6 = 6[1]
A has a charge of 4+, so number of electrons = 6 − 4 = 2[1]
There is a large difference between the 5th and 6th ionisation energies: the 6th electron is removed from an inner electronic shell. A has 5 valence electrons, so it is in Group 15.[1]
Element A is arsenic.[1]
The element to the right is selenium. Its first ionisation energy involves removing one of a pair of 4p electrons, which experiences inter-electronic repulsion.[1]
Less energy is needed to remove this electron from Se than the unpaired 4p electron from As, so the first ionisation energy of Se is lower.[1]
Al2+ has a greater nuclear charge than Na (more protons). The shielding effect is the same for Al2+ and Na, as they have the same electronic configuration and both lose the single 3s electron.[1]
Hence, Al2+ has a greater effective nuclear charge: its 3s electron experiences a greater electrostatic attraction to the positive nucleus, and more energy is required to remove it, leading to a greater third ionisation energy than the first ionisation energy of sodium.[1]
Cu+: 1s2 2s2 2p6 3s2 3p6 3d10[1]
Zn+: 1s2 2s2 2p6 3s2 3p6 3d10 4s1[1]
The second ionisation energy of Cu involves removing a 3d electron [½]. The second ionisation energy of Zn involves removing a 4s electron [½].
The 3d subshell is closer to the nucleus than the 4s subshell [½], so the electron removed from Cu experiences greater electrostatic attraction towards the nucleus [½]. More energy is required to remove it, so the second ionisation energy of Cu is greater.
The first ionisation energy of Kr is higher than that of Br.[1]
Kr has a larger nuclear charge, and its electrons are added to the same quantum shell, so the shielding effect is relatively constant. Kr has a greater effective nuclear charge: the attraction between the nucleus and the outermost electron is stronger, so more energy is required to remove it.[1]
There is a large increase from the 5th to the 6th ionisation energies, so the 6th electron is removed from an inner principal quantum shell, which is nearer to the nucleus.[1]
A has 5 valence electrons, so it is in Group 15 and is phosphorus.[1]
[1]
Amount of O = 1.994 − 1.0016 = 0.062125 mol[1]
Each SO2 contains one S atom and two O atoms, so amount of S = 0.0621252 = 0.0310625 mol. Let the mass of 32S be x g.
x32 + 1.00 − x34 = 0.0310625[1]
x = 0.898
Percentage by mass of 32S = 0.8981.00 × 100% = 89.8%[1]
Ar = 95.02(31.972) + 0.75(32.971) + 4.21(33.968) + 0.02(35.967)100
= 32.06 (2 d.p.)[1]